Extrusion of metals



EXTRUSION F METALS John Alan Tennant, Joseph Gordon Lauder, and ReginaldJames Barnard Naisbitt, Prescot, Henry Charles Woolley, Whiston, andAnthony Lawrenson, Prescot, England, assignors to British InsulatedCallenders Cables Limited, London, England, a British companyApplication November 13, 1951, Serial No. 255,946

Claims priority, application Great Britain November 28, 1950 4 Claims.(Cl. 2074) This invention relates to presses for the extrusion of metalof the kind in which a hot billet of metal is inserted in a cylinder andis forced by a ram advancing in the cylinder from one end thereof topass, by plastic flow in front of the ram, through a shaping passage (adie or dies) to form the extruded article (hereinafter referred to asbillet presses). The invention deals both with the extrusion of singlebillets and with the extrusion of a series of billets inserted andextruded in succession to form a long extruded body or series of bodies.The term extruded in succession means that the extrusion of the residueof a billet which remains in the press when extrusion is temporarilyinterrupted for reloading with a fresh billet is succeeded, as acontinuous process, by the extrusion of part or all of the fresh billet.

The invention is not concerned with the shape of the bodies extruded(they may for instance be tubes or the sheaths of electric cables) andis applicable to presses for the extrusion of metals in general. It isparticularly useful in presses dealing with aluminium and its alloys.

In the extrusion of single billets, there is a danger that air will betrapped between the billet and the cylinder wall. This danger arisesbecause the billet, in order to be freely inserted, must be of adiameter less than that of the cylinder and, on being pressed forward bythe ram is upset to spread to the full bore of the cylinder. In theextrusion in succession of billets the additional problem arises ofensuring complete union between the residue of the old charge left inthe cylinder at the end of the stroke of the ram and the new billetwhich is inserted in the cylinder after the withdrawal of the ram. Inboth cases it is found that there is considerable risk of the productionof occlusions of compressed air in the extruded metal. If this metalforms the comparatively thin wall of a tube, the body of occluded airmay be in such a position and at such a pressure that it can burst themetal lying between it and the surface of the tube. In any case thepresence of the occluded air is a source of weakness to the extrudedbody.

The improved press is provided with a passage opening into the cylinderconnected to means for producing a vacuum. This passage may open intothe cylinder in the region occupied by the billet or, when the press isonly to be used for the extrusion of billets in succession, in theregion between the end of the cylinder and the outer end of the billet.When the extrusion die is blocked by the residue of the previous billet,immediately the ram enters the cylinder evacuation of air commences.When the die is open, however, it may not be possible to evacuate thespace between the new billet and the cylinder until extrusion hascommenced, since the front end of the billet may not make an air tightjoint with the cylinder. Under these circumstances it is essential thatthe passage should enter the cylinder in the region occupied by thebillet.

Wherever the passage is located it is liable to receive nited StatesPatent O Patented July .10, 1956 small quantities of metal into its end.The passage is preferably so designed that a rod can be pushed throughit in order to clear it and prevent accumulation. A prodding rod can bepermanently located in the outer part of the passage and automatic meansoperated by external mechanism provided for operating it.

The vacuum passage is formed in the wall of the cylinder, preferably ina straight line about at right angles to the inner surface of the wallof the cylinder. It is found that a comparatively small hole willsufiice to efiect good evacuation.

A horizontally opposed double-acting billet press for extruding cablesheaths in accordance with the invention will hereinafter be describedwith reference to the accompanying drawings in which Figure 1 is anelevation in cross-section, in the direction in which the cable sheathis extruded, and Figure 2 is an elevation in cross-section on the lineIIII in Figure 1.

The press cylinders are two co-axial cylindrical bores 1 and 2 in ametal block 3. Extrusion of the cable sheath is in a direction atright-angles to the axes of the cylinders 1 and 2 and is effected by thesimultaneous movement of the two rams 4 and 5 towards each other byhydraulic or other means. In the drawings, the extrusion chamber isoccupied by the residue 6 of a charge and new billets 7 and 8 have beeninserted in the cylinders 1 and 2 in contact with the residue 6.

Referring to Figure 2, the extrusion die 9 is held in position in theblock 3 by a die block 10. A cable core 11 which is being sheathedpasses, during extrusion, in a direction from left to right through ahollow mandel 12, also mounted in the block 3, and is formed with asheath 18.

From Figure 1 it will be seen that immediately the rams 4 and 5 enterthe cylinders 1 and 2 they effect substantial enclosure of the spacesbetween their leading surfaces and the surfaces of the residue 6. Thesespaces are partly filled by the billets 7 and 8 but since the billetscannot fit tightly into the cylinders there are gaps in which air mightbe occluded between the cylindrical surfaces of the billets and thecylinder walls. Gaps may also exist between the inner faces of thebillets and the faces of the residue 6.

Two bores 13 and 14 opening into cylinders 1 and 2 are drilled throughthe block 3. These bores are connected through a pipe 15 to a vacuumpump (not shown).

During the extrusion process a film of metal may be formed on the innersurfaces of the cylinders by metal escaping backwards past the rams.Since this film may obstruct the passages 13 and 14, provision is madeto enable them to be cleared, comprising stop cocks 16 and 17 throughwhich a rod may be inserted.

The vacuum pump connected to the pipe 15 is started as the rams 4 and 5approach the cylinders 1 and 2 and thus, immediately the rams enter thecylinders, evacuation of the air spaces in the cylinders will becommenced. The vacuum is maintained by the pump until the rams 4 and 5have advanced past the passages 13 and 14, that is until the rams areabout to make contact with the billets 7 and 8 and commence theextrusion operation. The residue 6 is first extruded and the extrusionof the billets 7 and 8 then proceeds.

What we claim as our invention is:

1. A billet press for extruding metal from a succession of billetscomprising at least one cylinder open at one end to receive a ram andleading at its other end to an extrusion orifice, a ram, means forforcing said ram into said cylinder, a straight passage extendingthrough the wall of said cylinder opening into said cylinder through anorifice of small diameter near the region occupied by the end of a newbillet adjacent the ram head when the new billet is in position incontact with the residue of the old charge, and adapted to receive meansfor clearing the passage, and means connected to said passage forproducing a vacuum.

2. A billet press for extruding metal from a succession of billetscomprising at least one cylinder open at one end to receive a ram andleading at its other end to an extrusion orifice, a ram, means forforcing said ram into said cylinder, a straight passage extendingthrough the wall of said cylinder opening into said cylinder through anorifice of small diameter between said open end and the region occupiedby the end of a new billet adjacent the ram head when the new billet isin position in contact with the residue of the old charge, and adaptedto receive means for clearing the passage, and means connected to saidpassage for producing a vacuum.

3. A billet press for extruding metal comprising at least one cylinderopen at one end to receive a ram and leading at its other end to anextrusion orifice, a ram, means for forcing said ram into said cylinderand for separating said ram and said cylinder by a distance sufficientto enable a solid metal billet to be inserted into the open end of saidcylinder, a straight passage opening into said cylinder through anorifice of small diameter and extending through the wall thereof spacedfrom the extrusion orifice a distance substantially equal to the lengthof said billet, means communicating with the passage normally sealingsaid passage from the atmosphere adapted to receive means for clearingthe passage and means connected to said passage for producing a vacuum.

4. A billet press for extruding metal from a succession of billetscomprising at least one cylinder open at one end to receive a ram andleading at its other end to an extrusion orifice, a ram for forcing saidram into said cylinder, and for separating said ram and said cylinder bya distance sufiicient to enable a solid metal billet to be inserted intothe, open end of said cylinder, a straight passage extending through thewall of said cylinder opening into said cylinder through an orifice ofsmall diameter near the, open end thereof, means communicating with thepassage, means sealing the communicating means from the atmospheremovable therein to clear the passage, and means connected to saidpassage for producing a vacuum.

References Cited in the file of this patent UNlTED- STATES PATENTS1,720,722 Dean July 16, 1929 2,074,856 Piercy et al Mar. 23, 19372,350,829 Scharfnagel June 6, 1944 2,639,809 Perry et al May 26, 19532,639,810 Doan May 26, 1953

1. A BILLET PRESS FOR EXTRUDING METAL FROM A SUCCESSION OF BILLETSCOMPRISING AT LEAST ONE CYLINDER OPEN AT ONE END TO RECEIVE A RAM ANDLEADING AT ITS OTHER END TO AN EXTRUSION ORIFICE, A RAM, MEANS FORFORCING SAID RAM INTO SAID CYLINDER, A STRAIGHT PASSAGE EXTENDINGTHROUGH THE WALL OF SAID CYLINDER OPENING INTO SAID CYLINDER THROUGH ANORIFICE OF SMALL DIAMETER NEAR THE REGION OCCUPIED BY THE END OF A NEWBILLET ADJACENT THE RAM HEAD WHEN THE NEW BILLET IS IN POSITION INCONTACT WITH THE RESIDUE OF THE OLD CHARGE, AND ADAPTED TO RECEIVE MEANSFOR CLEARING THE PASSAGE, AND MEANS CONNECTED TO SAID PASSAGE FORPRODUCING A VACUUM.